Geoscience Reference
In-Depth Information
As in the granite areas of West Cornwall (Area 1), mineral mining activities have
had a strong impact on the area, and derelict tin mine buildings are scattered over much
of the landscape. The china-clay industry has also produced significant changes to the
scenery, one of the most remarkable sites being the workings 3 km northeast of St Aus-
tell (
a2
). These pits now house the famous Eden Project, an educational charity provid-
ing a 'Living Theatre of People and Plants' and attracting over a million visitors each
year (Fig. 67).
FIG
67.
The Eden Project is situated in a former china-clay pit. (Copyright Dae Sasitorn &
Adrian Warren/www.lastrefuge.co.uk)
The present-day pattern of streams and their valleys has evolved from ancestral
streams and valleys that carved most of the inland scenery over millions of years. In
the general section of this chapter, we have seen the remarkable way that the drainages
of the rivers Tamar and Exe flow southwards across most of the Southwest Region to
the sea, divided by the high ground of Dartmoor. A general tilt of the Region to the
south, and the resistance of the granite domes to stream and valley erosion, appear to
have been important factors. Closer examination of the drainage patterns shows that
the streams and valleys of the Bodmin Moor granite tend to radiate out from near its
centre, but that the distinctly larger Dartmoor granite has eroded down to form two
drainage divides, one in the north and one in the south. This may simply be a matter of
the different size of these two granite areas, which has allowed a more complex drain-
age pattern to develop through time over Dartmoor.
The parallel groups of incised valleys that are common in the granites of Area 1
are not clearly developed on Bodmin Moor and not visible at all on Dartmoor. It is in-
triguing that the fault system that was responsible for the parallel valleys further to the
west is not present in these larger eastern granites. This may tell us something about
the greater depth of weathering and erosion experienced by the eastern granites.
